Electronic organ employing time position multiplexed signals

ABSTRACT

An electronic organ including a counter acting as a source of twelve repetitive time position multiplexed signals, each derived at a different time on a different lead, one time position being provided for each note nomenclature of the musical scale, time positioned pulses being gated through respective key switches having the same nomenclature as respective time position slots. All time positioned signals passed by any octave of key switches are combined on a single octave output lead assigned to that octave, and signals on octave output leads are selectively combined by coupler logic, output signals derivable from the coupler logic network being combined with pulse position signals derived directly from the source to provide coincident gate signals which cause tone source signals to be fed via tone color filters to an output load.

United States Patent 11 1 11] 3,916,750 Uetrecht 5] *Nov. 4, 1975ELECTRONIC ORGAN EMPLOYING TIME 3,696,201 10/1972 Arsem et al. 84/1.01 ST MULTIPLEXED SIGNALS 3,697,661 10/1972 Deutsch.; 84/ 1.01 3,743,7557/1973 Wats0n.... 84/101 Inventor: Dale M- Uetrechl, Clncmnatl, ohlo3,746,773 7/1973 Uetrecht..... 84/1.01 3,755,608 8/1973 Deutsch 84/].01[73] Ass'gnee' Baum Company cmcmnat" 3,763,364 10/1973 Deutsch et al84/1.03 x

[ Notice: The portion of the term of this P i r Examiner-Stephen J.Tomsky P n q to y 17, 1990 Assistant ExaminerStanley J. Witkowski hasbeen dlsclalmed- Attorney, Agent, or FirmHyman Hurvitz [22] Filed: July3, 1973 21 App]. No.: 376,189 [57] ABSTRACT I An electronic organincluding a counter acting as a Related Apphcahon Data 7 source oftwelve repetitive time position multiplexed [62] Dlvlslo" 223,629, 4,1972, signals, each derived at adiiferent time on a different lead, onetime position being provided for each note nomenclature of the musicalscale, time positioned [52] US. Cl.2 84/]..01; 8471.03; 84/117 pulsesbeing gated through respective key Switches [51] hit. Cl. G10 1/00having the Same nomenclature as respective time i [58] Field of Search84/1.0l, 1.02, 1.03, 1.1, on Slow All time i i ned signals passed by any84/117 445 octave of key switches are combined on a single octave outputlead assigned to that octave, and signals [56] References C'ted onoctave output leads are selectively combined by ITED ST S PATENTScoupler logic, output signals derivable from the cou- 3,594,487 7 1971Jones, Jr. 84/l.l p logic tw rk ng m n d with pulse position 3,610,79910/1971 Watson 84/ 1.01 signals derived directly from the source toprovide co- 3,6l0,800 0/ 97 ut ch 8 1.0 incident gate signals whichcause tone source signals 3,647,929 3/1972 Mime 34/1-01 to be fed viatone color filters 'to an output load. 3,674,907 7/1972 Derry 84/1.0l3,683,096 8/1972 Peterson et al 8 1/103 x 6 Claims, 6 Drawin Figures 127 1 KEY 5 KEY sumcH E SLUHCHES MULTIPLEXER 5 Ha 12a 3 1 p 11111111;-PULSE ,gggjg cnuouza LOGlC. og s r ogi KEY sumcu i: DEMULTlPLEXER IAUDID TONE GATES GENERRTDRS TONE CDLDR FILTERS ands AB SLUI'TCHlNG U.S.Patent KEY I sumcHEs' COUPLER SUJFTCHES Nov. 4, 1975 Sheet 1 of 53,916,750

[23 5 KEY sumcH MULTIPLEXER 5 Ha \2a. Mumm PULSE COUPLER LDCflC. p o sngngx 1 KEY SUMTCH E DEMULTWLEXER 5 K18 AUDlD TONE GATES eemmmnrzs TONECDLDR F|LTERS and; TAB smrrcume U.S. Patent Nov. 4, 1975 Sheet 4 of53,916,750

U.S. Patent Nov.4, 1975 Sheet5 0f5 3,916,750

229m 522 swiismv Dmja ou Jdz m .Illllllll ELECTRONIC ORGAN EMPLOYINGTIME POSITION MULTIPLEXED SIGNALS CROSS-REFERENCE TO A RELATEDAPPLICATION This application is a division of application Ser. No.223,629, filed Feb. 4, i972, and now US. Pat. No. 3,746,773.

BACKGROUND Many prior art electronic organs have employed key switches,which control gates which serve to transfer tone signal from tone signalsources to an amplifier and loudspeaker. A lead is provided for eachnote of the organ, and since leads must be provided for connecting thetone sources of the organ to the gates, and the outputs of the gates totone signal collection buses, an

enormous footage of wire is employed in each organ, and a large numberof soldered connections.

Any organ of some degree of sophistication requires octave couplers,which are essentially networks for causing to sound notes an octaveabove or below that called for by a given key, or notes otherwiserelated tonally to the called for note may be required to sound in placeof the called for note.

It is an object of the present invention to transmit signals indicativeof the fact that key switches are closed on a time division multiplexbasis, in order to eliminate most of the wire leads of an organ, andthereby reduce its cost and complexity. Any system of multiplexing whichis utilized in a sophisticated electronic organ must have provision foroctave coupling. In accordance with the present invention twelve timepositioned pulses are generated, each time position being allocated to anote nomenclature, and each separate octave of keys of the organtransmitting via a separate octave lead, the time positioned pulseswhich indicate which key nomenclatures are played within that ctave.

It follows that for a 61 note keyboard, which is usual, six octave leadsare required, each carrying one or more of 12 time positioned pulsesrepresenting the 12 semitones of that octave, and that provision must bemade for the 61st note. The fact that all notes of a given nomenclatureare represented by the same time slot of the time division multiplexedsignals provides a practical opportunity for octave coupling, bytransfer of timed pulses from one octave lead to another.

SUMMARY A time division multiplex system for controlling the tone signalgates of an electronic organ, wherein to each octave of notes of theorgan is allocated one lead, over which the twelve notes of that octaveare transmitted as time position multiplexed note pulses, therebyreducing wiring costs in production of an organ, and transferring notepulses from one octave lead to another in order to achieve octavecoupling.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a signal flow diagram of a systembroadly according to the invention;

FIGS. 2a and 2b together comprise a circuit diagram, largely schematicof an organ including the features of FIG. I;

FIG. 3 is a block diagram of a pulse position source which applies timemodulated signals to the multiplexer of FIGS. 1 2;

FIG. 4 is a circuit diagram illustrating an octave of keying circuits;and

FIG. 5 is a schematic circuit diagram of demultiplex gates employed inthe system of FIGS. 1 3, inclusive DETAILED DESCRIPTION Referring toFIG. 1 of the accompanying drawings, 11 is a source of sequentialpulses, for example a clock driven counter, which provides pulses on 12output leads lla, each lead being connected to one stage of the counter,so that the pulses on the spatial array of leads 11 occur on a timedivision basis, each lead having its own time slot. The leads llaproceed to a multiplexer 12, which selects the pulses of each group of12 according to which key of an octave of keys is actuated and steers itto an output lead 12a, on a per octave basis, so that signals on anylead 12a can have any one of 12 positions representing notenomenclatures, the lead itself being identified with a specific octave.

The signals fed to multiplexer 12 from source 11 are selectively fedthrough the multiplexer in response to activation by the organist of keyswitches 14. In a typical organ, having an upper and lower manual and aset of foot pedals, 154 key switches are provided. Each of the upper orswell manual and lower or grand manual includes five octaves of keys,each of which includes 12 semi-tones, in addition to a key for C of theoctave immediately above or below the lowest or highest full octave. Keyswitches, in one embodiment of the invention, are provided for two fulll2 semi-tone) pedal octaves, plus eight semi-tones for the octaveadjacent the highest pedal full octave.

Key switches 14 are connected to multiplexer 12 in such a manner as togate all of the notes for a particular octave in each manual to adifferent output lead of the multiplexer. Therefore, for the exemplarysituation presented supra multiplexer 12 includes 15 output leads 12a onwhich are selectively derived pulse position signals in accordance withactivation of the key switches 14.

The fiften output leads of multiplexer 12 are fed to coupler logicnetwork 15 which is also responsive to settings of coupler switches 16made by the organist. Coupler switches 16 control interconnectionsbetween the 15 output leads of multiplexer 12 so that signals fromdifferent octaves can be coupled together. Coupler logic network 15includes a relatively small number of output leads, one for each octaveof each manual of the organ. In a typical organ, of the type described,there are 19 output leads of coupler logic network 15, one for each ofthe 15 output leads of multiplexer 12, one for the pedal super coupledoctave, one for the lower manual super coupled octave, one for the uppermanual super coupled octave, and one for the upper manual subcoupledoctave. On each of the 19 output leads of coupler logic network 15,there are selectively derived 12 pulse position signals indicative ofthe 12 semi-tones in each octave.

The output signals of coupler logic network 15 are combined with thepulse position signals derived from source 11 in decoder ordemultiplexer l3. Decoder 13 includes one coincidence gate for each toneof each of the 19 octave outputs of 15. The coincidence gates arearranged by octaves so that all of the gates of one octave areresponsive to the output lead of coupler logic network 15 which isdesignated for that octave. Within each octave,a coincidence gate isprovided for each semi-tone. Like semi-tone coincidence gates of theseveral octaves aredriven in parallel by the same pulse position outputsignal of source 11, whereby at any time all of the gates having thesame semi-tone nomenclature'are enabled by an output signal of source11. In response to time coincidence between the signal supplied toeachgate of decoder 13 by source 11 and coupler logic network 15, acontrol signal is generated to enable a selected one of gates 17.

Oneor more of gates 17 is provided for each of the organ tones. Gates 17include circuitry for converting (fil te ring) the relatively highfrequency coincidence outputs of decoder 13 into d.c. gating voltagesfor controlling the passage of signals from generators 18 to the outputof the gates. Signals from generators 18 are passed because the lengthof time a key is depressed relative to the frequency of pulses derivedfrom source 11 is such thatat least several hundred pulses are derivedfrom decoder 13 for each activation of one of key switches 14. Each D.C.gating voltage controls a multiplic it'y of audio gates of 17, one foreach footage to be tone colored. A typical manual would have 16, 8', 4',

12% and available. Thus audio signals would be QgatBd'frOmoneDC. gatingvoltage. ,QThe signals derived from gates 17 are fed to conventionaloutput circuitry including tone color filters and a tab switchingnetwork 19. Network 19 drives amplifier 20, which in turn feedsloudspeaker 21.

Reference isnow made to FIGS. 2a and 2b of the drawings wherein isillustrated a block diagram of a portion of the circuitry associatedwith deriving the control signals for the swell output. In FIG. 2a,shift register 31 is illustrated as including 12 different output ,leads 12 1 132. One of leads 121 132 is provided for Leach of thesemi-tones of an octave. The pulse position signals derived on leads 121132 occur in timed se- .quence so that there is no overlap between anyof the pulses and each has its own individual time slot that is uniquetothe time slot of all of the other pulses. To prevent the possibilityof overlap between the pulses derived on leads 121 132 shift register 31includes circuitrywhe'reby ,the duty cycle of the pulse derived on eachoftheleads is approximately per cent less than one part in 12. Thepulses derived on leads 121 132 areassigned the l2 semi-tone notedesignations in ac- L cordance with:

TABILEI Lead No.

121 122 I23 I24 I25 I26 I27 I28 I29 I30 131 132 Designation Themultiplexing pulses sequentially derived on leads switches for the uppermanual are respectively indicated by reference numerals 141-145, whilethe switches for the lower manual key switches 36 and the pedal switches37 are respectively indicated by reference numerals 146 and 147. Tofacilitate the description, separate leads to the different octaves ofthe lower manual and pedal switches or multiplexers are not illustrated.

The 12 signals applied to each octave of key switches are combined on asingle output lead. Thereby, the signals derived on the output leads ofeach of the key switches has a time position indicative of the activatedor depressed key in the octave. If more than one key in a particularoctave is depressed, a plurality of time position pulses are derived atthe output of each of the key switches, at times dependent upon thenomenclature of the depressed key. Since a key is invariably depressedfor a time interval approaching or exceeding a significant portion of asecond, a large number of pulses having the same relative time positionis derived for each key activation.

In addition to the five octaves of key switches included in the upperand lower manuals, these manuals include a further key switch, indicatedby reference numeral 148a for the upper manual, to provide the 61 keysin each manual. Key switch 148a and the corresponding key switch for thelower manual are connected to output lead 121 of shift register 31 sothat a high C note can be derived. The high C note has the same timeposition as the C notes derived for the other octaves.

The five octaves of signals derived from key switches for multiplexer146 are derived onleads 151-155. The single lead for the partial octave(for the note C) on the lower manual is derived on lead 156.

The two full octaves of notes derived from pedal switches of multiplexer147, are derived on leads 161 and 162, while the partial, eight-noteoctave is derived on lead 163.

Consideration will now be given to the specific circuitry in couplerlogic networks 41, 42 and 43. Coupler logic network 41 includes l8selectively energized inverting amplifiers 171-188. Amplifiers 171-188are arranged in three sets of six, whereby power is supplied to the sixamplifiers of each set simultaneously. If no power is supplied to theamplifiers of a particular set, the amplifiers can be considered as opencircuited switches. In response to power being supplied to theamplifiers, they function as unity gain, inverting amplifiers and can beconsidered as closed circuited switches. Power is supplied to amplifiers171-188 through three normally open circuited coupler tab switches191-193. In response to the organist closing any of the coupler tabswitches 191-193 power is supplied to a selected six of the invertingamplifiers to activate them into a closed state. Amplifiers 171-188 areconnected to be responsive to closure of coupler tab switches 191-193 sothat there is coupling to the next adjacent higher footage octave ofeach of the octaves associated with switches 141-145 and 148 in responseto closure of switch 191. There is coupling to the same octave inresponse to closure of switch 192, while there is coupling to the nextadjacent lower footage octave in response to closure of switch 193. Tothese ends, power is supplied to amplifiers 171- 176 in response toclosure of switch .191; power is supplied to amplifiers 177-182 inresponse to closure of switch 192; and

closure of switch 193. A convenient packaging arrangement for theamplifi- The outputs of amplifiers for similarly designated ocersincluded in coupling matrices 41-43 involves the taves of coupler logicnetwork 41 are connected to like use of multiple integrated circuitinverting amplifiers, output signals, in accordance with: each mountedon a single integrated chip and having a TABLE II 7' Output Octave 0. l2 3 4 5 6 7 Am lifier 183(3a) l77(2a) mus 7 I72( la) 173 (la) 174(la),175(la) 176(18) Amplifier I l84( 3a) 178(2a) 179(2a) 180(2a) l8l(2a)182(2a) Amplifier 185(3a) 186(321) 187(3a) 188(3a) In Table II, thenumbers in parenthesis indicate the common power supply terminal. Oneparticular, presunit order values for the activated coupler tabswitches, ently available integrated circuit chip includes six amthenumbers running in ascending order from O to 7 inplifiers therebyrendering it particularly adapted for use dicate the eight outputoctaves of coupler logic netin conjunction with the present invention.These ampliwork 41, and the three digit numbers indicate the referfiershave open collector outputs allowing them to sink ence numerals for theamplifiers. Hence, e.g., Table 11 current to the negative supply only ifthey are energized indicates that in response to coupler tab switch 193from the coupler tab and turned on from the time mulbeing closed, theoutput signals derived from key tiplexed key switch input. These opencollector outputs switches 141-145 are fed to the output leads for theoccan then be wired OR without using additional logic taves from O to 5via amplifiers 183-188. gates.

Coupler logic network 42 includes 12 amplifiers Demultiplexer or decoder13, FIG. 1, is illustrated in 201-212 arranged similarly to the couplingamplifiers FIG. 2a as including seven sets of AND gates (coinciof logicnetwork 41. Inverting amplifiers 201-212 are dence gates) 251 257. Eachset of AND gates 251 responsive to two additional coupler tab switches257 includes 12 individual AND gates, one for each of 221-222 whichenergize the amplifiers so that they sethe semi-tones of a completeoctave. AND gate sets lectively operate as open and closed circuitedswitches. 251 257 are respectively responsive to the output sig- Outputleads of amplifiers 201-212 are connected to nals derived for the sevenlowest octaves (0,1,2, 3,4,5

A output leads corresponding with those of amplifiers and 6) derived bycombining the outputs of coupler 171-182. The particular connectionsbetween these logic networks 41 43. The individual gates withinamplifiers and the output leads are given by: each set of AND gates 251257 are responsive to the TABLE 111 Output Octaves l 2 3 4 5 6 7 Amlifier 207(2b) 20l( lb) 202(lh) 203(lb) 204(lb) 205(1b) 2()6( lb)Amplifier v 208(2b) 209(2b) 210(2b) 211(2b) 212(2b) In Table III, thenumbers in parenflhesis indicate which amplifiers are responsive tocoupler tab switches 221 -222, whereby those amplifiers responsive toswitch 221 are indicated by (lb) and those responsive to switch 222 areindicated by (2b).

Couplerlogic network 43 includes six selectively energized invertingamplifiers 231-236, arranged in two sets of three. Power is selectivelyapplied to the two sets of amplifiers in response to closure of couplertab switches 241-242. Amplifiers 231, 232 and 233 provide coupling tothe higher footage outputs, and amplifiers 234-236 provide coupling tothe outputs at the same footages as coupled through switches 147 toleads 161-163. Connections between the output leads of amplifiers231-236 and control of the amplifiers in response to activation of theselected ones of coupler tab switches 241-242 is in accordance with:

12 pulse position signals derived on leads 121 132, as coupled throughdriver amplifiers 261. The AND gates in each of sets 251 257 respond tothe signals fed thereto from driver amplifiers 261 and the combinedoutput leads of coupler logic networks 41, 42 and 43 to derive d.c.gating signals that enable audio tones from tone generators 91 97 to beselectively passed through the sets of audio gates 281 287 to network19, FIG. 1.

In addition to the seven sets of 12 AND gates, a further AND gate 271 isprovided. AND gate 271 is responsive to the octave number 7 outputderived by combining the signals of coupler logic networks 41 43 and theCnote output signal by shift register 31 on lead 121. AND gate 271responds to coincidence between the octave number 7 input thereof andthe signal on TABLE IV lead 121 to derive an enable signal that gatesthe output Output Octave of tone generator 98 through audio gate 288 tocircuit 1 2 3 4 19. Amplifier 23400 Blue) 232( m 233 1c) Reference isnow made to FIG. of the drawing Amplifier 235( 2c) 236(2c) wherein thereis illustrated an embodiment for an oscillator and shift register thatderives the pulse position or 12 phase signal. Basically, the 12 phasesource includes In Table IV, the numbers in parenthesis designate a freerunning transistorized multivibrator 301 which which of coupler tabswitches 241-242 is depressed, drives a plurality of cascaded bistableflip-flops, that in whereby (1c) designates activation of coupler switchturn drive a logic network 300 having 12 output leads 241 and (2c)designates coupler switch 242. for deriving the 12 phase or pulseposition signal.

Transistorized multivibrator 301 is of conventional design and derives asquare wave voltage at terminal 302, with a frequency, for example, of240 KHz. The

square wave voltage developed at terminal 302 is shaped into a series ofpositive and negative pulses, one of which is derived in response toeach transition of the square wave by differentiator 303. The negativegoing pulses derived by differentiator 303 are amplified by driver 304which feeds toggle flip-flop 305 in parallel with input terminals of ANDgates 306 and 307. Flipflop 305 includes a true output terminal (O)which drives the other input terminal of AND gate 306 in parallel withclock input terminals (C) of J K flip-flops 308 310.

Flip-flops 308 310 are cascaded with each other so that they, in effect,form a three-stage counter, having a maximum count of eight. Connectionsbetween flipflops 308-310 enable them to function as a divide-bysixring'counter responsive to the voltage developed at the Q outputterminal of flip-flop 305. Because of the toggle action of flip-flop305, the flip-flops 305 and 308-310 effectively form a divide-by-12counter, or frequency divider for'the 240 KHz output of multivibrator301. To provide feedback required to establish the divide-by-six countfromthe counter including flipflops 308-.310, AND gate 311 is provided.AND gate 311 includes input terminals responsive to signals developed attrue output terminals (C) and (D) of flipflops 309-310 and develops anoutput signal that is supplied to the K input terminal of flip-flop 308,the J input terminal of which is responsive to the completively) offlip-flop 305 and the output of driver 304, in-

cludes l2 three-input NAND gates 32l332. Threeinput NAND gates 321-332respond to the output signals of gates 306 and 307 and signals developedat the true and complementary output terminals of flip-flops 308-310to'derive a 12 phase, pulse position signal, in such a manner that eachpulse has a duty cycle of approximately lO percent less than one part in12. The signal derived at the output terminal of each NAND gate is in anonoverlapping time position relative to the signal derived at each ofthe other NAND gates, and each of the signals is equispaced fromadjacent signals.

The connections between gates 306 and 307 and the output terminals offlip-flops 308-310 and input terminals of NAND gates 321-332 are givenby:

8} i TABLE V-continued I VI'NPUT SIGNALS ACD NAND GATE In Table V, theoutputs of gates306 and 307 are respectively denominated as A and A; thesignals derived responsive to a pulsating output of one of gates 306 andI 307, as indicated in Table V by the inclusion of an A or A inputsignal to each of the NAND gates.

Reference is now made to FIG. 4 of the drawings wherein is illustrated apreferred embodiment of a typical octave of key switches, such as thefirst octave 41 of upper manual key switches 35. The octave of keyswitches includes 12input leads, one for each semitone of an octave andeach responsive to a different one of the signals on leads 121-132,asderived from NAND gates 321-332. Each of leads 341-352 is connectedthrough a separate key switch 361-372 to the input terminal'of invertingamplifier 373. One'of the key switches 361-372 is provided for each ofthe keys of the octave being considered. Only one switch is provided foreach of the keys, regardless of the tab coupling which might be desiredfor a particular key be cause of the inclusion of matrices 41-43. Toprevent sneak .currents, each of key switches 361-372 is connected inseries with a different one of diodes 374, biased in such a manner as topass the negative going multiplexing signals supplied to leads 341-352by NAND gates 321-332. Because the multiplexing signals are supplied toleads 341-352 in different time positions, the waveform developed on thesingle output lead of amplifier 373, which is responsive to signalssupplied to all of leads .341-352, is, in effect, time positionmodulated by the depression of key switches 361-372. t

In FIG. 5 of the drawings is illustrated a portion of the circuitryincluded within one of the groups of l2 AND gates, such as group or set257 ofAND gates. in FIG. 5, complete circuitry is given for the C gateincluded in group 257, while fragmentary circuitry is given for the Bgate. 1

TheC gate includes NPNtransistor 391, having a base electrode responsiveto a positive going multiplexing pulse derived by the driver invertingamplifier 261, responsive to the signal on lead 121, while the B gatecomprises NPN transistor 392 having a base electrode responsiveto themultiplexing pulse derived by the driver, inverting amplifier 261responsive to the signal on lead 132. The emitters of transistors 391and 392 have a c'ommo n connection to .1000, ohm resistor 393 that isresponsive to a negative going pulse derived by the Number 6 output leadof a matrix comprising networks 41-43. The emitter collector path oftransistor 391 is biased to a conducting state with a duty cycle of tenpercent lessthan one part in 12, the same duty cycle as the multiplexingpulses, in response to the positive and negative multiplexing pulsesapplied to its base and emitter electrodes. The 20 KHZ, low duty cycleactivation of the emitter collector path of transistor 391' is convertedinto a dc. gating potential for tone generator sources connected toterminals 394 and 395 by connecting a relatively large, 0.33 microfaradcapacitor 396 between the collector of transistor 391 and ground.Capacitor 396 serves as a bias for slow attack and fast attack gatingcircuits for the tone signals supplied to terminals 394 and 395.

The slow attack circuit for the tone supplied to tenninal 394 includes aresistive voltage divider comprising two 100 kilohm resistors 397 and398, the junction of which is connected to the cathode of diode 399,having an anode that is biased through resistor 401. The tone source atterminal 394 is connected to the other terminal of resistor 398 and isselectively coupled through diode 399 to tone color circuits 319. Thetone signal supplied to tenninal 394 is a square wave voltage havingvariations between 15 volts and +23 volts, voltages which enableselective coupling through the anode cathode path of biased diode 399.

If there is no time coincidence between the positive and negative pulsessupplied to the base and emitter of transistor 391, the square wavevoltage at terminal 394 alternately charges and discharges capacitor 396between a pair of voltage levels, both of which are sufficiently high tomaintain diode 399 in a back biased condition. In response to transistor391 being forward biased at 20 KHz rate with a low duty cycle ofapproximately one part in 12, the charge on capacitor 396 is reduced,with a resulting decrease in the voltage across the capacitorelectrodes. In response to the reduced voltage across the electrodes ofcapacitor 396, the dc. voltage level at the cathode of diode 399 isreduced sufficiently to enable the square wave tone signal at tenninal394 to be passed through diode 399 to tone color circuit 319.

To provide fast attack in response to activation of transistor 391 intoa conducting state, the tone signal at terminal 395 is selectivelycoupled to the collector of transistor 391 via resistors 402 and 403,which are connected in series with the parallel combination of resistor404 and capacitor 405. A junction between resistors 402 and 403 isconnected to the cathode of diode 406, the anode of which is connectedto a +1 5 volt d.c. biasing source at terminal 407 via resistor 408. Thevoltage of the tone source connected to terminal 395 has a differentfrequency than the tone source connected to terminal 394 but variesbetween volts and +23 volts so that diode 406 functions in a similarmanner to diode 399. The time required for the source connected toterminal 395 to be coupled through diode 406 is considerably less thanthat required for the source connected to terminal 394 to be coupledthrough diode 399 because of the inclusion of capacitor 405 in thecircuit between terminal 395 and the collector of transistor 391.Typically, the time constant of the fast attack circuit is milliseconds,a result achieved by selecting the values of resistors 403 and 404 to be47 kilohms, the resistance of resistor 402 to be 100 kilohms, and thevalue of capacitance 405 to be 0.33 microfarads.

In general more than one audio gate would be connected to the slow andfast attack bias. Only one each are shown for simplicity. For example,if three sets of gates are connected to the collector of transistor 391.10 andthree sets ofgates are connected to terminal 409, capacitors 396and 405 would beincreased to one microfarad and resistors 393 and 404would be reduced to 330ohms and l5 kilohms respectively. This scalingwould'maintain the same time constant or attack rate as in the exemplarycase.

In this general case, generator tones at 16', 8, 4', 2 2', and 1 can bekeyed on responsive to coupler gates 175, 182, 205 and 212. The lowerfootages (l6, 8 and 4) on the slow attack and the higher footages (2 2',and l) on the fast attack.

It is to be understood that similar circuits are connected in thecollector circuit of transistor 392 and are selectively activated inresponse to simultaneous application of positive and negativemultiplexing pulses to the base and emitter thereof. Simultaneousapplication of the multiplexing pulses to the base and emitter oftransistor 392 results in passing B tones from tone generator sourcesconnected in fast and slow attack circuits in the collector thereof inthe manner described with regard to the slow and fast attack circuits oftransistor 391.

What is claimed is:

1. In a multiplex organ system, a key switch for each note of amulti-octave manual, means for converting actuated ones of the keys ofeach octave of said manual separately into only 12 pulse codings inconcurrent octaval note frames which occur in common for the separateoctaves, and means for converting the codings of said pulses to tones ofsaid organ.

2. The combination according to claim 1, wherein is included means forconverting the codings of pulses in one note frame pertaining to oneoctave of said organ to tones of a different octave of said organ.

3. An electronic multi-octave organ, comprising a multi-octave array ofkey switches, a source of 12 coded pulses, each of said pulses occupyinga predetermined time slot corresponding with a note nomenclature on atime division multiplex basis, a plurality of channels correspondingrespectively with different octaves of said organ, means responsive toselective actuations of said key switches for selecting said codedpulses for transmission in said channels, an array of tone signalsources, a load, and means responsive to the pulses selected fortransmission in said channels for concurrently applying to said loadtone signals corresponding selectively with different footages of saidorgan. I

4. An electric organ, comprising an array of key switches, a source of12 sequential pulses each occupying a predetermined time slot on a timedivision multiplex basis and each time slot corresponding with all keysof a given nomenclature, a plurality of leads each corresponding with adifferent octave of keys of said organ, means responsive to selectiveactuation of said key switches for selecting said pulses fortransmission on said leads to convey the selected pulses according tothe octave of each actuated key and its note nomenclature, an array oftone signal sources, a load circuit, and means responsive to said pulsesfor applying to said load circuit tone signals of pitch according to thetime positions of said pulses and the leads on which said pulses occur.

5. The combination according to claim 4, wherein is included means fortransferring pulses from one of said channels to another one of saidchannels at will.

6. In an electronic organ having plural octaves of keys, means forconverting notes of a first octave of 12 said second octave, a sequenceof tone signal sources. and means for selectively applying said groupsof pulses to control said tone signal sources to provide tone signalscorresponding with said actuated ones of said keys. l

1. In a multiplex organ system, a key switch for each note of amulti-octave manual, means for converting actuated ones of the keys ofeach octave of said manual separately into only 12 pulse codings inconcurrent octaval note frames which occur in common for the separateoctaves, and means for converting the codings of said pulses to tones ofsaid organ.
 2. The combination according to claim 1, wherein is includedmeans for converting the codings of pulses in one note frame pertainingto one octave of said organ to tones of a different octave of saidorgan.
 3. An electronic multi-octave organ, comprising a multi-octavearray of key switches, a source of 12 coded pulses, each of said pulsesoccupying a predetermined time slot corresponding with a notenomenclature on a time division multiplex basis, a plurality of channelscorresponding respectively with different octaves of said organ, meansresponsive to selective actuations of said key switches for selectingsaid coded pulses for transmission in said channels, an array of tonesignal sources, a load, and means responsive to the pulses selected fortransmission in said channels for concurrently applying to said loadtone signals corresponding selectively with different footages of saidorgan.
 4. An electric organ, comprising an array of key switches, asource of 12 sequential pulses each occupying a predetermined time sloton a time division multiplex basis and each time slot corresponding withall keys of a given nomenclature, a plurality of leads eachcorresponding with a different octave of keys of said organ, meansresponsive to selective actuation of said key switches for selectingsaid pulses for transmission on said leads to convey the selected pulsesaccording to the octave of each actuated key and its note nomenclature,an array of tone signal sources, a load circuit, and means responsive tosaid pulses for applying to said load circuit tone signals of pitchaccording to the time positions of said pulses and the leads on whichsaid pulses occur.
 5. The combination according to claim 4, wherein isincluded means for transferring pulses from one of said channels toanother one of said channels at will.
 6. In an electronic organ havingplural octaves of keys, means for converting notes of a first octave ofsaid organ into time positions of first pulses occupying those of 12time positions corresponding with actuated ones of the keys of saidfirst octave, means for converting notes of a second octave of saidorgan into time positions of further pulses occupying those of said 12time positions corresponding with actuated ones of keys of said secondoctave, a sequence of tone signal sources, and means for selectivelyapplying said groups of pulses to control said tone signal sources toprovide tone signals corresponding with said actuated ones of said keys.